TY - CHAP A1 - Selgrad, Kai A1 - Müller, Jonas A1 - Stamminger, Marc ED - Giachetti, Andrea ED - Biasotti, Silvia ED - Tarini, Marco T1 - Faster Ray-Traced Shadows for Hybrid Rendering of Fully Dynamic Scenes by Pre-BVH Culling T2 - Smart Tools and Apps for Graphics - Eurographics Italian Chapter Conference N2 - With ever increasing ray traversal and hierarchy construction performance the application of ray tracing to problems often tackled by rasterization-based algorithms is becoming a viable alternative. This is especially desirable as the ground truth for these algorithms is often determined by using ray tracing and thus directly applying it is the simplest way to generate images satisfying the reference. In this paper we propose a very efficient pre-process to speed up the construction and traversal of sub-optimal, but fast-to-build hierarchies used for interactive ray tracing and show how it can be applied to shadow rays in a hybrid environment, where ray tracing is used to sample area lights for scene positions found and shaded via rasterization. Y1 - 2015 SN - 978-3-905674-97-2 U6 - https://doi.org/10.2312/stag.20151295 PB - The Eurographics Association ER - TY - CHAP A1 - Lier, Alexander A1 - Selgrad, Kai A1 - Stamminger, Marc ED - Alberto Riva, T1 - DIY Meta Languages with Common Lisp T2 - Proceedings of the 10th European Lisp Symposium (ELS 2017), Vrije Universiteit Brussel, Brussels, Belgium, April, 3-4 2017 N2 - In earlier work we described C-Mera, an S-Expression to C-style code transformator, and how it can be used to provide high-level abstractions to the C-family of programming languages. In this paper we provide an in-depth description of its internals that would have been out of the scope of the earlier presentations. Œese implementation details are presented as a toolkit of general techniques for implementing similar meta languages on top of Common Lisp and illustrated on the example of C-Mera, with the goal of making our experience in implementing them more broadly available. KW - Macros KW - Code Generation KW - Common Lis KW - Meta Programmin Y1 - 2017 UR - https://selgrad.org/publications/2017_els_LSS.pdf SN - 978-2-9557474-1-4 SP - 72 EP - 79 PB - ACM CY - New York, NY, USA ER - TY - CHAP A1 - Selgrad, Kai A1 - Lier, Alexander A1 - Wittmann, Markus A1 - Lohmann, Daniel A1 - Stamminger, Marc T1 - Defmacro for C: Lightweight, Ad Hoc Code Generation T2 - Proceedings of ELS 2014 7th European Lisp Symposium ; May 5 - 6 2014, IRCAM, Paris, France N2 - We describe the design and implementation of CGen, a C code generator with support for Common Lisp-style macro expansion. Our code generator supports the simple and efficient management of variants, ad hoc code generation to capture reoccurring patterns, composable abstractions as well as the implementation of embedded domain specific languages by using the Common Lisp macro system. We demonstrate the applicability of our approach by numerous examples from small scale convenience macros over embedded languages to real-world applications in high-performance computing. KW - Meta Programming KW - Code Generation KW - Common Lisp KW - Configurability KW - Macro KW - Maintenance Y1 - 2014 UR - https://european-lisp-symposium.org/static/proceedings/2014.pdf SN - 2677-3465 SP - 80 EP - 87 ER - TY - CHAP A1 - Lier, Alexander A1 - Stamminger, Marc A1 - Selgrad, Kai T1 - CPU-Style SIMD Ray Traversal on GPUs T2 - Proceedings of the Conference on High-Performance Graphics N2 - In this paper we describe and evaluate an implementation of CPU-style SIMD ray traversal on the GPU. We show how spreading moderately wide BVHs (up to a branching factor of eight) across multiple threads in a warp can improve performance while not requiring expensive pre-processing. The presented ray-traversal method exhibits improved traversal performance especially for increasingly incoherent rays. KW - GPU KW - ray tracing KW - SIMD Y1 - 2018 SN - 9781450358965 U6 - https://doi.org/10.1145/3231578.3231583 SP - 1 EP - 4 PB - Association for Computing Machinery CY - New York, NY, USA ER - TY - CHAP A1 - Laux, Lea A1 - Erdődi, László A1 - Selgrad, Kai T1 - Trust as the Elephant in the Room: Security Evaluation of Decentralized Online Social Networks with Mastodon T2 - Norsk IKT-konferanse for forskning og utdanning N2 - Federated online social networks are an alternative to centralized and often profit-driven social networks. Instead of providing exactly one main platform, federated and decentralized approaches consist of multiple platforms, nodes or instances, leading to new challenges for guaranteeing confidentiality, integrity and availability. In addition, privacy is taken into close consideration due to the sensitive nature of processed personal data and the purpose of online social networks as well as the user behavior on social media. The recent popularity and broad use of the federated micro-blogging platform Mastodon issues the matter of security and privacy challenges for this type of architecture and the specific platform as well. Mastodon is part of a larger network called Fediverse with several platforms with different purposes. Communication and interoperability between Fediverse platforms is mostly achieved by ActivityPub protocol as standard for decentralized social networking, defined by W3C. We analyze Mastodon as the currently most prominent and largest example of a Fediverse platform. Therefore, we perform tests for typical types of software vulnerabilities as well as evaluate common security challenges built into its design. As a result, we identify trust as security principle as critical issue, leading to multiple weak points such as enabling attackers and malicious actors to spread misleading information as well as network availability impacts. We suggest possible solutions customized to our findings as well as general security recommendations when building a federated online social network such as the Fediverse KW - Federated Online Social Networks KW - Security Evaluation KW - Security Design Review Y1 - 2023 UR - https://www.ntnu.no/ojs/index.php/nikt/article/view/5653 IS - 3 ER - TY - CHAP A1 - Baumann, Timo A1 - Pohl, Martin A1 - Selgrad, Kai ED - Schäfle, Claudia ED - Dölling, Hanna T1 - Einführung und erste Evaluation des Selbstlernkonzepts CodeClinic an der OTH Regensburg T2 - Tagungsband MINT Symposium 2025. Zukunft MINT Lehre: Was bleibt? Was kommt? Was wirkt? N2 - Mit der CodeClinic wollen wir das Programmieren-Lernen – eine der großen Einstiegshürden in Informatik- und informatiknahen Studiengängen – in einen Prozess überführen, der das gemeinschaftliche Lernen in der Hochschullehre stärker als bisher in den Vordergrund rückt. Davon profitieren Studierende in ihrer fachlichen und persönlichen Entwicklung, und das Lernumfeld spiegelt die tatsächliche Realität der beruflichen Praxis besser wider. Wir unterstützen dieses Konzept durch einen für selbstgesteuertes und gemeinschaftliches Lernen ausgelegten SCALE-UP-Raum, den wir an der OTH Regensburg eingerichtet haben. In unserem Beitrag erläutern wir Konzept und Raum und liefern eine erste Evaluation zum Erfolg unserer Maßnahmen. KW - Hochschuldidaktik KW - Programmierung KW - Studieneingangsphase KW - SCALE-UP KW - Lernen durch Lehren (LdL) KW - BayernMINT Y1 - 2025 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-86138 SN - 1612-4537 PB - BayZiel – Bayerisches Zentrum für Innovative Lehre CY - München ER -